166
Dinosauria and Reptiles All dinosaurs were probably uricotelic animals which
had to use the extrarenal way of excreting excess of monovalent ions. It is suggested
(Osmolska 1979 ) that they were able to use the nasal salt gland for this purpose. Its
presence may have been especially important for unloading the excess of potassium
ions ingested by large herbivores with their vegetarian food, or for getting rid of
sodium ions by herbivores living in a saline environment.
A salt-secreting gland was fi rst demonstrated in marine reptiles by Schmidt- Nielsen
and Fänge ( 1958b ). These scientists showed that a gland situated in the orbit of the
eye was capable of elaborating a secretion with twice the sodium concentration of
sea water. Thus, the salt gland is an organ for excreting excess salts in such recent
marine reptilians as crocodiles (Dunson 1970 ; Taplin and Grigg 1981 ; Taplin et al.
1982 ; Cramp et al. 2007 , 2008 , 2010a , b ), iguanas (Dunson 1969 ; Hazard 2004 ), sea
snakes (Taub and Dunson 1967 ) as well sea turtles (Ellis and Abel 1964 ; Abel and
Ellis 1966 ; Kooistra and Evans 1976 ; Hudson and Lutz 1986 ; Lutz 1997 ; Reina and
Cooper 2000 ; Reina et al. 2002 ).
Saltwater crocodiles ( Crocodylus porosus ) possess very specialized lingual salt
glands. Peculiarities of osmotic challenge based on function of these glands are still
unknown. Recently, Cramp et al. ( 2010a , b ) studied the regulation and distribution
of the Na
+ /K
+ -ATPase (NKA) pump. These authors paid special attention to the
a -(catalytic) subunit in the salt glands of C. porosus specimens, which were
permanently acclimated during six months to freshwater (FW) or 70 % seawater (SW).
Here, the results reported by these authors:
– “the NKA was immunolocalised to the lateral and basal membrane of secretory
cells;
– the NKA alpha-subunit was 2-fold more abundant in SW-acclimated C. porosus
salt glands.
– NKA gene expression was elevated in the salt glands of SW- vs FW-acclimated
crocodiles.
– no increase in the specifi c activity of NKA in SW-acclimated animals;
– the proportion of tissue oxygen consumption rate attributable to NKA activity
was not different between SW- and FW-acclimated animals;
– the salt glands of SW-acclimated animals were larger than those of FW-acclimated
animals;
– there were signifi cantly more mitochondria per unit volume in secretory tissue
from SW-acclimated animals;
– crocodiles possess the capacity to moderate NKA activity following prolonged
exposure to SW” (Cramp et al. 2010a , b ).
It can be suggested (Cramp et al. 2008 ) that the salt glands of saltwater crocodiles
are phenotypically plastic, both from morphological and physiological view and
play crucial adaptive role in acclimatization of these unique reptiles to different
levels of salinity.
Interesting phenomenon has been reported by Hazard ( 2001 ) concerning the ability
of nasal salt glands of some lizards to secrete potassium as well as sodium, in the
form of chloride or bicarbonate. A single lizard, the Galapagos lizard ( Amblyrhyiichus
3 Biocomposites and Mineralized Tissues
Dinosauria and Reptiles All dinosaurs were probably uricotelic animals which
had to use the extrarenal way of excreting excess of monovalent ions. It is suggested
(Osmolska 1979 ) that they were able to use the nasal salt gland for this purpose. Its
presence may have been especially important for unloading the excess of potassium
ions ingested by large herbivores with their vegetarian food, or for getting rid of
sodium ions by herbivores living in a saline environment.
A salt-secreting gland was fi rst demonstrated in marine reptiles by Schmidt- Nielsen
and Fänge ( 1958b ). These scientists showed that a gland situated in the orbit of the
eye was capable of elaborating a secretion with twice the sodium concentration of
sea water. Thus, the salt gland is an organ for excreting excess salts in such recent
marine reptilians as crocodiles (Dunson 1970 ; Taplin and Grigg 1981 ; Taplin et al.
1982 ; Cramp et al. 2007 , 2008 , 2010a , b ), iguanas (Dunson 1969 ; Hazard 2004 ), sea
snakes (Taub and Dunson 1967 ) as well sea turtles (Ellis and Abel 1964 ; Abel and
Ellis 1966 ; Kooistra and Evans 1976 ; Hudson and Lutz 1986 ; Lutz 1997 ; Reina and
Cooper 2000 ; Reina et al. 2002 ).
Saltwater crocodiles ( Crocodylus porosus ) possess very specialized lingual salt
glands. Peculiarities of osmotic challenge based on function of these glands are still
unknown. Recently, Cramp et al. ( 2010a , b ) studied the regulation and distribution
of the Na
+ /K
+ -ATPase (NKA) pump. These authors paid special attention to the
a -(catalytic) subunit in the salt glands of C. porosus specimens, which were
permanently acclimated during six months to freshwater (FW) or 70 % seawater (SW).
Here, the results reported by these authors:
– “the NKA was immunolocalised to the lateral and basal membrane of secretory
cells;
– the NKA alpha-subunit was 2-fold more abundant in SW-acclimated C. porosus
salt glands.
– NKA gene expression was elevated in the salt glands of SW- vs FW-acclimated
crocodiles.
– no increase in the specifi c activity of NKA in SW-acclimated animals;
– the proportion of tissue oxygen consumption rate attributable to NKA activity
was not different between SW- and FW-acclimated animals;
– the salt glands of SW-acclimated animals were larger than those of FW-acclimated
animals;
– there were signifi cantly more mitochondria per unit volume in secretory tissue
from SW-acclimated animals;
– crocodiles possess the capacity to moderate NKA activity following prolonged
exposure to SW” (Cramp et al. 2010a , b ).
It can be suggested (Cramp et al. 2008 ) that the salt glands of saltwater crocodiles
are phenotypically plastic, both from morphological and physiological view and
play crucial adaptive role in acclimatization of these unique reptiles to different
levels of salinity.
Interesting phenomenon has been reported by Hazard ( 2001 ) concerning the ability
of nasal salt glands of some lizards to secrete potassium as well as sodium, in the
form of chloride or bicarbonate. A single lizard, the Galapagos lizard ( Amblyrhyiichus
3 Biocomposites and Mineralized Tissues